From household appliances to infrastructure, a power semiconductor has been used for various products at the present time. FIG. 4 illustrates an example of a semiconductor package. A semiconductor package 10b is often manufactured by a process for connecting a semiconductor element 104 and a substrate such as a lead frame 102 by solder 106 containing Pb and Sn, providing a wiring line using a wire 107, and covering an entire portion by a resin 101. Recently, it becomes necessary to use solder not containing Pb from a concern about an environment and the development of the Pb-free solder is promoted. As alternative materials substituting for the Pb solder, Bi, Au, Ag, and Zn solders are considered.
Meanwhile, when the semiconductor package is used for vehicle installation, the semiconductor package is placed in an environment more severe than a conventional vehicle interior, such as an engine room and on-engine. That is, high-reliability products in which performance is maintained for a longer time in a high temperature, high humidity, and high vibration environment are demanded.
The life of various bonding portions is important to the reliability of the semiconductor package, but the reliability of the semiconductor package is often limited by adhesion of the lead frame and the molding resin. For example, in the case in which a semiconductor package having insufficient reliability is used, if the semiconductor package is used during a long period in a high temperature and high humidity environment, the adhesion in a bonded interface of the lead frame and the molding resin is deteriorated and the lead frame and the resin are separated from each other. The separation causes the excessive thermal stress to be generated in a soldered portion of the semiconductor element, so that a crack extension of the solder is accelerated or water permeates into a separation portion to corrode the solder or the element. As a result, the semiconductor package is failed in time shorter than the original life. Therefore, improvement of the adhesion of the lead frame and the resin becomes important to improvement of the life of the product.